An aircraft wing of a commercial aircraft or jetliner is typically assembled prior to being attached to a fuselage of the aircraft. For example, an aircraft wing assembly typically includes a front spar and a rear spar each of which extends in the span direction of the wing, and structural members such as, for example, stringers and ribs that connect to the front and rear spar to form a skeletal structure or framework of the aircraft wing. A wing panel or skin, which may be formed with stringers, is coupled to the skeletal structure or framework to form an aircraft wing.
To couple or attach the aircraft wing to the fuselage, commercial aircrafts employ wing-fuselage attachment joints. For example, a wing-fuselage joint couples an aircraft wing to a central wing box supported by the fuselage of the aircraft. The aircraft wing is often attached to the central wing box via an upper wing panel joint and a lower wing panel joint. Typically, an upper wing panel joint employs a double plus chord composed of aluminum to couple an upper wing panel of the aircraft wing to the central wing box and a lower wing panel joint employs a T-chord to couple a lower wing panel of the aircraft wing to the central wing box.
Further, because of their relatively high strength-to-weight ratios, composite materials such as carbon-fiber reinforced plastics are often used in aircraft wings to reduce weight and increase performance. For example, the upper and lower wing panels of an aircraft wing or central wing box may be composed of a carbon composite or carbon fiber reinforced polymer, while wing spars, ribs and other frame structures are manufactured from metallic materials such as aluminum, steel, etc.
However, directly attaching carbon composites such as carbon-fiber reinforced plastics to aluminum structures can induce corrosion (e.g., galvanic corrosion) due to chemical and electro-chemical reactions with the surrounding environment. For example, composite materials such as carbon fibers are good electrical conductors and they produce a large galvanic potential with the aluminum alloys of an airplane structure. Thus, corrosion can occur when moisture forms on a composite/aluminum interface due to significantly different electrochemical potentials of these materials. Therefore, in some instances, coupling a composite wing panel directly to a plus chord composed of aluminum may cause an undesirable corrosive effect at that joint. Plus chords composed of titanium protect against such undesirable corrosive effect, but significantly increase the costs of the aircraft.